Known braking systems of the general type under consideration include at least one pressure line for carrying compressed air from at least one pressurized compressed air source to a brake device, and a brake pedal for receiving brake commands from a vehicle driver and for operating a brake line, which can be connected to the brake device. Such systems are used in trucks as well as in other vehicle types.
Trucks are often equipped with driving assistance systems that also include systems that actively control braking performance. With the aid of various sensors, such brake assist systems register the driving situation at any given time and, in specific situations, undertake braking operations according to the evaluation of these data. In each case, this is effected without active intervention on the part of the vehicle driver. In order to preclude negative influences on vehicle handling, control of the braking performance by the brake assist systems is discontinued as soon as the driver issues a brake command via the brake pedal. In known systems, the existence of a brake command on the part of the driver is registered by a pressure sensor, for example, that monitors the line pressure on the rear axle circuit or the front axle circuit of the vehicle. If this sensor registers the presence of a brake pressure, the control is discontinued and the full pressure controlled by the driver is transmitted to the vehicle trailer.
A disadvantage of such known braking systems is that simultaneous feedback control by the brake assist system and active braking ordered by the driver is not possible. Likewise, a quantitative determination of the brake pressure to be transmitted to the trailer is not possible in such known braking systems.